We've seen large-scale mass noncompliance in numerous instances. The ATF has reported fewer than 500 bump-stocks turned in. "Assault rifle" registrations in Connecticut and New York are estimated at only 5-10% of the actual number possessed. Only about a dozen "high capacity" magazines were registered in New Jersey.
This mirrors the situations in Australia and the UK, in which compliance is well under 20%.
That's all well and good, of course, unless I'm the one who gets singled out. Just because my neighbors and friends are getting away with it doesn't mean I will. Maybe someone in the HOA has it in for me, or I have a vengeful spouse who decides to call the authorities.
Then what? I get arrested. If I resist in any way, or the SWAT team doesn't feel like taking chances, things get ugly. They'll brand me as a domestic terrorist on the news to "make an example." It's doubtful I can expect any leniency from the courts.
In the wake of things like the New York SAFE Act, the cry of "I won't comply" has become somewhat popular, and the lack of police action on the matter makes people dangerously complacent on stuff like this.